EFFECT OF DISJOINING PRESSURE ON SPREADING OF LIQUID DROPLET CONTAINING SURFACTANT OVER CORRUGATED TOPOGRAPHY SURFACE

For the spreading of an insoluble surfactant-laden droplet over corrugated topography, a disjoining pressure model induced by the concentration of the surfactant was established. The lubrication theory was applied to derive the evolution equations of droplet height and interfacial surfactant concentration and the droplet spreading characteristics under disjoining pressure were numerically simulated. Results indicate that under the effect of disjoining pressure, the evolution time of droplet is shortened significantly, and the spreading rate is accelerated. At the advancing front of the droplet, the number of wavelet tends to decrease obviously, which improves the stability of spreading. In addition, the effect of disjoining pressure on droplet spreading stability is closely related to surfactant concentration associativity. Reducing the attraction strength coefficient α₁ promotes the spreading of droplet. Conversely, decreasing repulsion strength coefficient α₂ exhibits the interfacial instability and enlarges the evolving disturbance energy resulting in spreading inhibited. Increasing height D or wave number k of corrugated topography slows down the spreading rate of the droplet.